cifs: don't attempt busy-file rename unless it's in same directory

Busy-file renames don't actually work across directories, so we need
to limit this code to renames within the same dir.

This fixes the bug detailed here:

    https://bugzilla.redhat.com/show_bug.cgi?id=591938

Signed-off-by: Jeff Layton <jlayton@redhat.com>
CC: Stable <stable@kernel.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/inode.c

@@ -1401,6 +1401,10 @@ cifs_do_rename(int xid, struct dentry *from_dentry, const char *fromPath,
 	if (rc == 0 || rc != -ETXTBSY)
 		return rc;
 
+	/* open-file renames don't work across directories */
+	if (to_dentry->d_parent != from_dentry->d_parent)
+		return rc;
+
 	/* open the file to be renamed -- we need DELETE perms */
 	rc = CIFSSMBOpen(xid, pTcon, fromPath, FILE_OPEN, DELETE,
 			 CREATE_NOT_DIR, &srcfid, &oplock, NULL,